Conventional endoscopes include a main body from which the lumen extends. The body contains one port for viewing the operation site through the lumen, and another port for supplying to the operation site illumination through the lumen. Yet another port is provided for suction/purging and the primary port receives the tools or laser beam with which the surgery is to be performed. In laser surgery the end of the articulated arm through which the laser beam propagates is connected to the primary port through a coupler which may be a straight coupler or a joystick coupler. The joystick coupler can be difficult and frustrating to use because of the extreme sensitivity of the joystick in controlling the beam. The coupler contains a lens which focuses the laser beam at a focal point on the central axis of and somewhat beyond the distal end of the lumen. The coupler and lens are universal devices which do not provide precise alignment of the lens with the lumen. As a result the aiming of the surgical laser beam is difficult and significant power can be lost. Often the lens aperture is larger than the input to the lumen so light energy is lost before the beam enters the proximal end of the lumen. In addition, the lens can be misaligned. If the beam arrives on axis from the articulated arm there will be little inconvenience as the on-axis beam will still be focused on the lumen axis. However, if, as is more commonly the case, the beam arrives off-axis, the misaligned lens will establish a laterally offset focal point which will cause "wall bounce". That is, the beam will ricochet off the walls of the lumen and result in a defocused, fuzzy beam with a serious loss of intensity so that the requisite operating power is lost and precise aiming is frustrating if not impossible.